Method of machining crankshaft

ABSTRACT

A method of machining a crankshaft from a workpiece whereby all of pin and journal portions of the workpiece are milled and thereby machined with a single crankshaft miller unit. The method comprises: establishing a phase position of the workpiece (3) with a phase positioning jaw (4c) that is provided in one of the chucks (4); clamping the workpiece (3) at its opposed ends with both the chucks (4); milling with a cutter (5e), thereby machining journal and pin portions of the workpiece (3) in succession; after all of the journal and pin portions are milled in the workpiece (3) except a first journal portion (J1) that is located at a position where the phase positioning jaw (4c) and the cutter (5e) may interfere with each other, unclamping the one chuck (4) provided with the phase positioning jaw (4c) and retracting that one chuck (4) to a position at which the jaw (4c) and the cutter (5e) may no longer interfere with each other; clamping again the workpiece (3) at its opposed ends with both the chucks (4); and thereafter milling and thereby machining the first journal portion (J1) with the cutter (5e).

TECHNICAL FIELD

The present invention relates to a method of machining a crankshaft asused in an engine.

BACKGROUND ART

A crankshaft as employed in an engine that can be mounted, e. g., in anautomobile has pins and journals typically milled and thereby machined,i. e., shaped, by a crankshaft miller in a workpiece.

A crankshaft shaping miller known in the art is described, e. g., inJapanese Unexamined Patent Publication No. Hei 6-297221.

A crankshaft miller as described in that publication makes use of acutter which is smaller in width than a pin and a journal of acrankshaft to be machined, in order to permit a workpiece with pin andjournal portions that vary in width to be machined by milling thoseportions each individually in a number of, say, six, divided steps.

The crankshaft miller to mill and thereby machine each of such pin andjournal portions in a workpiece also requires the workpiece to bepositioned with respect to an angle of rotation thereof, thus a phaseposition thereof.

Such phase positioning is effected by preliminarily machining areference seat provided for this purpose in the one of counter weightportions that is located at one end of a workpiece and then, before theworkpiece is introduced into the crankshaft miller and is clamped at itsopposed ends each with a chuck, by bringing the phase positioningreference seat on the workpiece in contact with a phase positioning jawlocated at one of the chucks.

The conventional crankshaft miller, however, makes it impossible tomachine the one of journal portions that is located adjacent to the endof the workpiece at which the reference positioning seat is provided,because of interference between the cutter and the phase positioning jawbrought in contact with the reference seat.

This has hitherto required such a journal portion to be machined in aseparate step using a separate machine tool such as a lathe. Poorproductivity results from the increased number of machining stepsnecessitated and an added cost of the equipment is incurred because ofthe use of separate equipment such as a lathe thus rendering the priorart disadvantageous.

It is accordingly an object of the present invention to provide a methodof machining a crankshaft from a workpiece whereby all of pin andjournal portions of the workpiece are milled or thereby machined with asingle crankshaft miller unit.

SUMMARY OF THE INVENTION

In order to achieve the object described above, there is provided inaccordance with the present invention as a first embodiment thereof, amethod of machining a crankshaft from a workpiece with its opposed endsclamped by a pair of chucks by a rotating cutter to mill and therebymachine journal and pin portions of the crankshaft workpiecesuccessively, which method comprises the steps of:

providing a phase positioning jaw in one of the said chucks;

establishing a phase position of the workpiece with the said phasepositioning jaw;

clamping the workpiece at its opposed ends with both the said chucks;

milling with the said cutter and thereby machining the Journal and pinportions of the said workpiece in succession;

after all of the journal and pin portions are milled and therebymachined in the said workpiece except a first journal portion that islocated at a position at which the said phase positioning jaw and thesaid cutter may interfere with each other, unclamping the one chuckprovided with the said phase positioning jaw and retracting the saidchuck to a position at which the said Jaw and the said cutter may nolonger interfere with each other;

clamping again the said workpiece at its opposed ends with both the saidchucks; and thereafter milling and thereby machining the said firstJournal portion with the said cutter.

The present invention also provides in a second embodiment thereof amethod of machining a crankshaft from a workpiece with its opposed endsclamped by a pair of chucks by a rotating cutter to mill and therebymachine journal and pin portions of the crankshaft workpiecesuccessively, which method comprises the steps of:

providing a phase positioning jaw in one of the said chucks;

clamping the workpiece at its opposed ends with both the said chucks ata position at which the said phase positioning Jaw and the said cuttermay not interfere with each other; thereafter milling and therebymachining a first journal portion in the said workpiece with the saidcutter;

unclamping the said both chucks and then advancing the said one chuckand establishing a phase position of the said workpiece with the saidphase positioning Jaw;

clamping again the said workpiece at its opposed ends with the said bothchucks; and thereafter milling and thereby machining all of the journaland pin portions other than the said first journal portion in the saidworkpiece in succession with the said cutter.

The present invention further provides in a third embodiment thereof amethod of machining a crankshaft from a workpiece with its opposed endsclamped by a pair of chucks by a rotating cutter to mill and therebymachine journal and pin portions of the crankshaft wqrkpiecesuccessively, which method comprises the steps of:

providing a phase positioning reference pin in one of the said chucks;

establishing a phase position of the workpiece with the said phasepositioning reference pin;

clamping the workpiece at its opposed ends with both the said chucks;and thereafter milling with the said cutter, and thereby machining thejournal and pin portions of the said workpiece in succession.

The present invention further provides in a fourth embodiment thereof amethod of machining a crankshaft from a workpiece with its opposed endssupported by a pair of centers and clamped by a pair of chucks by arotating cutter to mill and thereby machine journal and pin portions inthe workpiece successively, which method comprises the steps of:

providing a phase positioning jaw in one of the said chucks;

establishing a phase position of the workpiece with the said phasepositioning jaw;

clamping the workpiece at its opposed ends with both said chucks; andthereafter milling with the said cutter, thereby machining the journaland pin portions of the workpiece in succession;

after all of the journal and pin portions are milled and therebymachined in the said workpiece except a first journal portion that islocated at a position at which the said phase positioning jaw and thesaid cutter may interfere with each other, unclamping the one chuckprovided with the said phase positioning jaw and retracting the saidchuck to a site at which the said jaw and the said cutter may no longerinterfere with each other;

clamping one of the said centers that is located proximal to the saidfirst journal with the said one chuck; and thereafter milling andthereby machining the said first journal with the said cutter.

The present invention also provides in a fifth embodiment thereof amethod of machining a crankshaft from a workpiece with its opposed endssupported by a pair of centers and clamped by a pair of chucks by arotating cutter to mill and thereby machine journal and pin portions inthe workpiece successively, which method comprises the steps of:

providing a phase positioning jaw in one of the said chucks;

clamping one of the said centers that is located proximal to a firstjournal portion of the workpiece with the one chuck provided with thesaid phase positioning jaw at a position at which the said phasepositioning jaw may not interfere with the said cutter and clamping thesaid workpiece at its opposite end with the other of the said chucks;thereafter milling and thereby machining a first journal portion in thesaid workpiece with the said cutter;

unclamping the said both chucks and then advancing the said one chuckand establishing a phase position of the said workpiece with the saidphase positioning jaw;

clamping again the said workpiece at its opposed ends with the said bothchucks; and thereafter milling and thereby machining all of the journaland pin portions other than the said first journal portion in the saidworkpiece in succession with the said cutter.

According to the present invention embodied in these forms, all ofjournal and pin portions in a workpiece can be machined with a singleunit of crankshaft miller; hence it becomes unnecessary to provide aseparate machine tool tailored and to carry out a separate machiningprocess stage required as in the prior art, to machine the first Journalportion in the workpiece.

Thus, the thereby reduced number of process stages required to machine acrankshaft enhances its productivity and the eliminated need for aspecial machine tool dedicated to machine the first journal portionreduces the cost of equipment for manufacture.

Also, the ability to machine all of journal and pin portions in asingle, given line of manufacture permits the line to be automated andunmanned. Then, the use of a multi-edge cutter with a multiplicity oftips, which provides a longer serviceable tool life than a single edgecutter, enhances the serviceability of a given crankshaft miller andresults in a consequential improvement in its productivity as well.

Of the forms of embodiment described, the first and second areadvantageously applicable to a workpiece with its pulley shaft elongatedwhereas the fourth and fifth are conveniently available for a workpiecewith its pulley shaft short in length. Such selective applicability oravailability of the embodiments of the method of the present inventionin accordance with particular workpiece configurations makes the use ofa given crankshaft miller highly flexible. In particular, where aworkpiece with a short pulley shaft is machined, the elongate center onthe side of the chuck retracted can be held clamped with a claw memberto prevent the latter from fluctuating in position under a reactiveforce in milling, thus permitting a first journal portion to be milledand thereby machined highly accurately.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will better be understood from the followingdetailed description and the drawings attached hereto showing certainillustrative embodiments of the present invention. In this connection,it should be noted that such embodiments as illustrated in theaccompanying drawings hereof are intended in no way to limit the presentinvention but to facilitate an explanation and understanding thereof.

In the accompanying drawings

FIG. 1 is a front view that illustrates one form of the crankshaftmiller with a part omitted for carrying out a method of the presentinvention;

FIG. 2 is an enlarged front view that illustrates a region of chucks inthe crankshaft miller shown in FIG. 1;

FIG. 3 is a side view that shows a structure shown in FIG. 2 as viewedin the direction of arrow III;

FIG. 4 is a cross sectional view of the structure shown and taken alongthe line IV-IV in FIG. 3;

FIG. 5 is a front view that shows the construction of a work restincluded in the crankshaft miller shown in FIG. 1;

FIG. 6 is a diagrammatic view shown to illustrate a first embodiment ofa crankshaft machining method according to the present invention;

FIG. 7 is a further diagrammatic view shown to illustrate furtherdetails of that embodiment;

FIG. 8 is a diagrammatic view shown to illustrate a second embodiment ofthe crankshaft machining method of the present invention;

FIG. 9 is a front view that shows another form of the crankshaft millerwith a part omitted for carrying out a method of the present invention;

FIG. 10 is a diagrammatic view shown to illustrate a third embodiment ofthe crankshaft machining method of the present invention;

FIG. 11 is an enlarged front view that shows a region of chucks in thecrankshaft miller shown in FIGS. 1 and 2, which are shown to carry aworkpiece having a short pulley shaft;

FIG. 12 is a diagrammatic view shown to illustrate a fourth embodimentof the crankshaft machining method of the present invention;

FIG. 13 is a further diagrammatic view shown to illustrate furtherdetails of that fourth embodiment;

FIG. 14 is a diagrammatic view shown to illustrate a fifth embodiment ofthe crankshaft machining method of the present invention;

FIG. 15 is a diagrammatic view that illustrates a machining procedureusing a crankshaft miller provided with a pair of cutter units; and

FIG. 16 is a diagrammatic view shown to illustrates a machining processof a crankshaft using that procedure.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, suitable embodiments of the present invention with respectto a combined machining apparatus and a crankshaft machining method byusing the same are set out with reference to the accompanying drawingshereof.

One example of the crankshaft miller shown in FIG. 1 in its front viewis suitable to practice a method of machining a crankshaft from aworkpiece according to the present invention.

The crankshaft miller shown in FIG. 1 has a bed 1 on which a pair ofwork heads 2 are mounted as movable towards and away from each other.

The work heads 2 are provided in their faces opposing to each other withchucks 4, respectively, which is adapted to carry a workpiece 3 byclamping its opposed ends, respectively, in which a journal portion 3aand a pin portion 3b is provided to be machined.

As shown in FIGS. 2 to 4, the chucks 4 each comprise a chuck body 4athat has about its center line a center 4b disposed as movable back andforth relative to the chuck body 4a. The centers 4b are adapted to befitted into center holes 3c formed respectively in the opposed endregions of the workpiece 3 to support the workpiece 3. Here, one of thechucks 4 includes a phase positioning jaw 4c that is adapted to bebrought into contact with a phase positioning reference seat 3e which isformed in a counter weight portion 3d of the workpiece located adjacentto one end thereof to establish a required phase position of theworkpiece 3. That one chuck 4 also includes a three-piece claw member 4dthat is adapted to clamp a pulley shaft 3f provided at one end of theworkpiece 3. And, the other chuck 4 includes another three-piece clawmember 4d that is adapted to clamp a flange 3g provided at the other endside of the workpiece 3. The workpiece 3 can be clamped thereby at itsopposed ends and fixed in position with these chucks 4.

On the bed 1 between the work heads 2 there are mounted a cutter unit 5and a work rest 6 each movably in a longitudinal direction of the bed 1.

The cutter unit 5 includes a saddle 5a in mesh with a ball screw,threaded shaft 8 that is rotatable by a drive motor 7 mounted on the bed1 at one end region thereof. The saddle 5a has a slide 5a mountedthereon that is movable in a direction orthogonal to a direction ofmovement of the saddle 5b.

The slide 5b is provided with a swing arm 5c having a cutter 5e mountedthereto. The cutter 5e is formed on its inner peripheral surface with anumber of tips 5d and is rotatable to mill or machine the workpiece 3with these tips 5d. The swing arm 5c is vertically swung and oscillatedby an oscillating mechanism not shown.

The work rest 6 as shown in FIG. 5 has a saddle 6a mounted on the bed 1movably by a drive means (not shown) and has, above the saddle 6a, apair of rest arms 6c supported pivotally on their respective supportshafts 6b so as to be capable of being mutually opened and closed. Theserest arms 6c are provided, respectively, on their opposing faces withrest holders 6d for supporting the journal portions 3a of the workpiece3 both upwards and downwards.

The opening sides of the rest arms 6c are adapted to be held closed bytwo sandwiching lock plates 10a of a lock mechanism 10 arranged on thesaddle 6a to prevent these rest arms 6c from opening while the workpiece3 is being machined.

Referring now to FIGS. 6 and 7, let us explain the first embodiment of acrankshaft machining method practiced with a crankshaft miller inaccordance with the present invention.

This embodiment of the machining method applies to a workpiece 3 withits pulley shaft 3f elongated as shown in FIG. 2 and such thatretracting the chuck 4 on the side of the pulley shaft may keep the clawmember 4d to remain engaged with the pulley shaft 3f.

The workpiece 3 is introduced between the chucks 4 in the crankshaftmiller and is supported by both centers 4b provided respectively thereinwith these centers 4b fitted in the center holes 3 at the opposed endsof the workpiece 3. Then, the phase positioning Jaw 4c that is providedin the chuck 4 on the side of the pulley shaft 3f is brought intocontact with the phase positioning reference seat 3e preformed in thecounter weight portion 3d of the workpiece 3, thereby establishing aphase position of the workpiece 3.

After the workpiece 3 is phase positioned, both claw members 4d in thechucks 4 are actuated to clamp respectively the pulley shaft 3f and theflange 3g of the workpiece 3 at the sites shown by the arrows in FIG. 6,thereby fixing the workpiece 3 in position.

In the process stages shown in FIG. 6, the fifth journal portion J5 thatis located closest to the flange 3g is first milled with the cutter 5eand thereby machined in the first process stage.

After the fifth journal portion J5 is machined completely, the cutter 5eis displaced to position ahead of the fourth pin portion P4. And, thework rest 6 is removed to position ahead of the fifth journal J5 thathas already been machined, which becomes supported by the work rest 6.The fourth pin portion P4 is now milled with the cutter 5e and therebymachined in the second process stage.

In the third process stage, the fourth journal portion J4 is milled andthereby machined with the fifth journal portion J5 still supported bythe work rest 6.

Next, the cutter 5e is displaced to lie ahead of the third pin portionP3 and the work rest 6 is removed to position ahead of the fourthjournal portion J4 having been machined to support the fourth journalportion J4. Then, the third pin portion P3 is milled with the cutter 5eand thereby machined in the fourth process stage.

Thereafter, with the operation likewise repeated, the third journalportion J3, the second pin portion P2, the second journal portion J2 andthe first pin portion P1 are milled and thereby machined in succession,in the fifth, the sixth, the seventh and the eighth process stages,respectively.

In the ninth process stage in which the first journal portion J1 must bemachined, the phase positioning jaw 4c that has been located in contactwith the phase positioning reference seat 3e preformed in the counterweight portion 3d does interfere with the cutter 5e, thereby preventingthe first journal portion J1 from being milled and thereby machined.

Then, here in the ninth process stage, the chuck 4 in which the pulleyshaft 3f is clamped is unclamped and the work head 2 lying on the sideof the unclamped chuck 4 is retracted.

It can then be seen that the elongated pulley shaft 3f of the workpiece3 ensures that that chuck 4 if retracted keeps the claw member 4d fromcoming out of engagement therewith.

The work head 2 is retracted to a position where the phase positioningjaw 4c may no longer interfere with the cutter 5e that is going tomachine the first journal portion J1 as shown in FIG. 7. With the workhead 2 so located, the chuck 4 is permitted to clamp the pulley shaft 3fagain, to allow the cutter 5e to commence milling, thereby machining thefirst journal portion J1 in the workpiece 3.

Then, after all the journal portions 3a and the pin portions 3b havebeen machined, both of the chucks 4 are unclamped to permit the machinedworkpiece 3 to be taken out and a new workpiece 3 to be introduced intothe crankshaft miller in order to be machined in the process with thedescribed stages repeated. Thus, the possibility is here realized toprovide a crankshaft with journals 3a and pins 3b all machined with asingle unit of crankshaft miller from each of the workpieces 3.

While in the first embodiment of the method of the invention described afirst journal portion J1 is machined in the ninth machining processstage, it should be noted that the first journal portion J1 can bemachined in the first machining process stage, i. e., before all theother portions are machined likewise, in a second embodiment of thepresent inventive method described in connection with FIG. 8 below.

Thus, in the second embodiment, the workpiece 3 introduced in thecrankshaft miller is not phase positioned first and, where the chuck 4on the side of its pulley shaft 3f is retracted, is clamped with theboth chucks 4 to allow its first journal portion J1 to be machined fist,i. e., in the first process stage.

Then, the workpiece 3 with the first journal portion J1 that has beenmachined is unclamped at its both end sides and the chuck 4 on the sideof the pulley shaft 3f is advanced to a position where the workpiece 3can be phase positioned with the phase positioning jaw 4c.

The workpiece 3 that has been phase positioned is then clamped to permititself to be machined, starting with its fifth journal portion J5 andthereafter continuingly in succession, as in the first embodimentdescribed.

And, ending with the first pin portion P1 in the ninth process stage,all the Journal portions 3a and the pin portions 3b have been machined.

While the arrangement described above advantageously applies to aworkpiece 3 with a pulley shaft 3f elongated, if the workpiece 3 has apulley shaft 3f not elongated, it follows that the chuck 4 on the sideof the pulley shaft 3f if retracted to a position where the phasepositioning jaw 4c may no longer interfere with the cutter 5e causes theclaw member 4d to be out of engagement with the pulley shaft 3f so thatthe workpiece 3 can no longer be clamped again.

Thus, a method of machining a crankshaft workpiece 3 even with a pulleyshaft 3f not elongated, that is embodied in another aspect in accordancewith the present invention is described below with reference to FIGS. 9and 10.

FIG. 9 shows a crankshaft miller that can be used to machine a workpiece3 with a pulley shaft 3f, either short or long whichever. Thiscrankshaft miller can be used with a workpiece 3 with a flange 3g havinga phase positioning hole 3h preformed in an end face thereof, and isarranged to include a chuck 4 for clamping the flange 3g on the side ofthe workpiece 3. That chuck 4 is provided on its end face with a phasepositioning reference pin 4e as a projection adapted to be fitted intothe phase positioning hole 3h preformed in the workpiece 3 so that theworkpiece 3 may then be phase positioned.

Referring now to FIG. 10, the crankshaft machining method is described,representing a third embodiment of the present invention using thecrankshaft miller shown in FIG. 9.

The workpiece 3 that is introduced between the chucks 4 in thecrankshaft miller is supported by the centers 4b therein with thesecenters fitted with the center holes 3c at the opposed ends of theworkpiece 3. Either the workpiece 3 or the chucks 4 can then be rotatedto permit the phase positioning reference pin 4e provided in the chuck 4for clamping the workpiece 3 at its flange 3g side to be fitted into thephase positioning hole 3h preformed in the workpiece 3. The workpiece 3can thus be phase positioned.

After the workpiece 3 is phase positioned, both the claw members 4d inthe chucks 4 are actuated to clamp the pulley shaft 3f and the flange 3gof the workpiece 3 at the sites, respectively, that are shown by thearrows in FIG. 10, thereby fixing the workpiece 3 in position.

In the first process stage shown in FIG. 10, the fifth journal portionJ5 that is located closest to the flange 3g is first milled with thecutter 5e and thereby machined.

After the fifth journal portion J5 is machined, the cutter 5e isdisplaced to position ahead of the fourth pin portion P4. And, the workrest 6 is removed to position ahead of the fifth journal J5 that hasbeen machined, which thus becomes supported by the work rest 6. Thefourth pin portion P4 is now milled with the cutter 5e and therebymachined in the second process stage.

In the third process stage, the fourth journal portion J4 is milled andthereby machined, with the fifth journal portion J5 still supported bythe work rest 6.

Next, the cutter 5e is displaced to lie ahead of the third pin portionP3 and the work rest 6 is removed to position ahead of the fourthjournal portion J4 having been machined to support the fourth journalportion J4. Then, the third pin portion P3 is milled with the cutter 5eand thereby machined in the fourth process stage.

Thereafter, with the operation likewise repeated, the third journalportion J3, the second pin portion P2, the second journal portion J2 andthe first pin portion P1 are machined in succession, in the fifth, thesixth, the seventh and the eighth process stages, respectively.

In the final, ninth process stage in which the first journal portion JIis to be machined with the cutter 5e, it is seen that the absence on thechuck 4 side for clamping the pulley shaft 3f of a phase positioning pinor anything else that may interfere with the cutter 5e permits the firstjournal portion J1 to be machined without the need to retract the chuck4.

Reference is next made to FIGS. 11 to 13 for the description of anothermethod of machining a crankshaft workpiece using the crankshaft millershown in FIG. 2.

This method applies to a workpiece 3 with its pulley shaft 3f notelongated such that retracting the chuck 4 on the side of the pulleyshaft 3f causes the claw member 4c to be out of engagement with thepulley shaft 3f, thus making it impossible to clamp the pulley shaft 3f.

The workpiece 3 is introduced between the chucks 4 in the crankshaftmiller and is supported by both the centers 4b provided respectively inthe chucks 4 with these centers 4b fitted in the center holes 3c at theopposed ends of the workpiece 3. Then, the phase positioning jaw 4cprovided in the chuck 4 on the side of the pulley shaft 3f is broughtinto contact with the phase reference seat 3e preformed in the counterweight portion 3d of the workpiece 3, thereby establishing a phaseposition of the workpiece 3.

After the workpiece 3 is phase positioned, both the claw members 4d inthe chucks 4 are actuated to clamp respectively the pulley shaft 3f andthe flange 3g of the workpiece 3 at the sites shown by the arrows A andB in FIG. 12, thereby fixing the workpiece 3 in position as shown inFIG. 11.

In the first process stage shown in FIG. 12, the fifth journal portionJ5 that is located closest to the flange 3g is first milled with thecutter 5e and thereby machined.

After the fifth journal portion J5 is machined, the cutter 5e isdisplaced to position ahead of the fourth pin portion P4. And, the workrest 6 is removed to position ahead of the fifth journal portion J5 thathas been machined, which then becomes supported by the work rest 6. Thefourth pin portion P4 is now milled with the cutter 5e and therebymachined in the second process stage.

In the third process stage, the fourth journal portion J4 is milled andthereby machined, with the fifth journal portion J5 still supported bythe work rest 6.

Next, the cutter 5e is displaced to lie ahead of the third pin portionP3 and the work rest 6 is removed to position ahead of the fourthjournal portion J4 having been machined to support the fourth journalportion J4. Then, the third pin portion P3 is milled with the cutter 5eand thereby machined in the fourth process stage.

Thereafter, with the operation likewise repeated, the third journalportion J3, the second pin portion P2, the second journal portion J2 andthe first pin portion P1 are machined in succession, in the fifth, thesixth, the seventh and the eighth process stages, respectively.

In the ninth process stage in which the first journal portion J1 needsto be machined, the phase positioning jaw 4c that has been located incontact with the phase positioning reference seat 3e preformed in thecounter weight portion 3d does interfere with the cutter 5e, therebypreventing the first journal portion J1 from being machined.

Then, here, in the ninth process stage, the chuck 4 in which the pulleyshaft 3f is clamped is unclamped. Then, with the workpiece 3 heldclamped at its both sides with the centers 4b in the both chucks 4, onlythe chuck 4 on the side of pulley shaft 3f is retracted to a position atwhich the phase positioning jaw 4c does not interfere with the cutter 5ethat is going to machine the first journal portion J1.

Then, where the chuck 4 is retracted to an extent such that the cutter5e does not interfere with the phase positioning jaw 4c, it can be seenthat while the shortness of the pulley shaft 3f prevents it from beingclamped by the the chuck 4 with the claw member 4d as shown in FIG. 13,the center 4b elongated towards the root end of the pulley shaft 3fpermits the claw member 4d of the chuck 4 to clamp the center 4b at asite on its elongated side and to prevent the center 4b thereby fromfluctuating in position.

The first journal portion J1 is now machined with the cutter 5e broughtinto a machining position therefor in the state that the work rest 6 isclamping the second journal portion J2 as in the eighth process stage.Then, the center 4b in the chuck 4 on the pulley shaft 3f side is thusprevented from fluctuating in position under a reactive force in millingthat is exerted thereon in this machining operation, thus permitting thefirst journal portion J1 to be milled and thereby machined highlyaccurately.

After all of the journal portions 3a and the pin portions 3b have beenmachined, the chucks 4 are unclamped to permit the machined workpiece 3to be taken out and a new workpiece 3 to be introduced into thecrankshaft miller in order to be machined in the process with thedescribed stages repeated. Thus, the possibility is here again ensuredto provide a crankshaft with journals 3a and pins 3b all machined with asingle unit of the crankshaft miller from an individual workpiece 3.

While in the preceding embodiment of the method of the invention, afirst journal portion J1 is machined here too in the ninth machiningstage, it should be noted that the first journal portion J1 can bemachined in the first machining stage, i. e., before all the otherportions are machined likewise, in a fifth embodiment of the presentinventive method described in connection with FIG. 14 below.

Thus, in this alternative embodiment, the workpiece 3 introduced intothe crankshaft miller and clamped at its both sides each with the center4b in each of the chucks 4, respectively, is not phase positioned first.And, where the chuck 4 on the side of its pulley shaft 3f is retractedso that the phase positioning jaw 4c may not interfere with the cutter5e for machining the first journal portion J1, the center 4b is clampedat a site on its elongated end side (as shown by the arrow A in FIG. 12)with the claw member 4d in the chuck 4 on the pulley shaft 3f side andthe flange 3g of the workpiece 3 is clamped (at a site as shown by thearrow B) with the chuck 4 on other side to permit the first journalportion J1 to be machined in the first process stage.

Then, after the first journal portion J1 has been machined in the firstprocess stage, the center 4b in the chuck 4 on the pulley shaft 3f sideis operated to unclamp the center 46 and the other chuck 4 is operatedto unclamp the workpiece 3. The chuck 4 on the pulley shaft 3f side isthen advanced to permit the workpiece 3 so unclamped to be phasepositioned with the phase positioning jaw 4c.

The workpiece 3 that has been phase positioned is then clamped again atits both sides with the chucks 4 to permit it to be machined, commencingwith its fifth journal portion J5 and thereafter continously insuccession, as in the fourth embodiment described previously.

And, ending with the first pin portion P1 in the ninth process stage,all of the journal portions 3a and the pin portions 3b have beenmachined.

These journal portions 3a and pin portions 3b machined in each ofprocess stages in embodiments of the method according to the presentinvention are shown in FIG. 14.

It should be noted at this point that if journal portions 3a and pinportions 3b to be machined are different in width and/or R-corneredgroove configuration, each individual journal, pin portion 3a, 3b can bemachined in a plurality of divided machining steps with a cutter 5e thatis smaller in width than the journals and pins. Otherwise, if they areidentical in configuration, a form type cutter can be used to machineeach of them in a single machining step.

Further, in a crankshaft miller provided with a pair of cutter units 5,e. g., one on the left hand side and the other on the right hand side inthe miller, a cutter 5e in one of them can be designed to be a roughmachining cutter with a cutter 5e in the other designed to be a finishmachining cutter, to machine each portion of a workpiece to in aplurality of steps, thereby permitting the need for a medium/finishmachining operation to be eliminated.

A machining procedure in which journal portions 3a and pin portions 3bare successively machined, each in a plurality of steps is describedbelow with reference to FIG. 15.

As shown in FIG. 15, a pin portion 3b is machined first for the opposingside surfaces a and b of the counter weight portions 3d located at itsboth sides and then for its outer peripheral surfaces c and d in twosteps.

Then, after the peripheral regions e and f of the opposing counterweight portions 3d are chamfered, the outer peripheral surface g of thecounter weight portion 3d of the journal portion 3a that is adjacent tothe pin portion 3b is machined.

Thereafter, as in the pin portion 3b, the opposing side surfaces h and iof the counter weight portions 3d at the both sides of the journalportion 3a are machined, the outer peripheral surfaces j and k of thejournal portion 3a are machined, the respective peripheral regions m andn of the both counter weight portions 3d are chamfered, and the outerperipheral surface o of the counter weight portion 3d that is adjacentto the journal portion 3a is machined.

With such a machining procedure likewise repeated, all of the journalportions 3a and the pin portions 3b are successively machined. FIG. 16shows in a chart a process of machining a crankshaft for use in a sixcylinder engine, using the machining procedure mentioned above.

In concluding the description, it should be noted that while in theseveral embodiments described, the cutter unit 5 and the work rest 6 arearranged to be displaced by separate drive means, respectively, it isnaturally possible to provide a coupling means between the cutter unit 5and the work rest 6 for uncouplably connecting them to enable a drivemeans for one of them, e. g., the cutter unit 5, to displace the other,e. g., the work rest 6.

It should also be noted that while the embodiments illustrated aredescribed in connection with a crankshaft miller arrangement in which aworkpiece 3 is fixed in position between a pair of chucks 4 while eachof journal and pin portions 3a and 3b is machined therein, the methodaccording to the present invention can likewise be embodied with ancrankshaft miller arrangement in which a workpiece 3 is rotated whileeach of journal and pin portions 3a and 3b is machined therein or acrankshaft miller arrangement with a cutter 5e having a multiplicity oftips 5d on its outer peripheral surface to mill and thereby machine aworkpiece 3.

While the present invention has hereinbefore been set forth with respectto certain illustrative embodiments thereof, it will readily beappreciated by a person skilled in the art to be obvious that manyalterations thereof, omissions therefrom and additions thereto can bemade without departing from the essence and the scope of the presentinvention. Accordingly, it should be understood that the invention isnot intended to be limited to the specific embodiments thereof set outabove, but to include all possible embodiments thereof that can be madewithin the scope with respect to the features specifically set forth inthe appended claims and encompasses all the equivalents thereof.

What is claimed is:
 1. A method of machining a crankshaft from aworkpiece with opposed ends of the workpiece clamped by a pair of chucksusing a rotating cutter to mill and thereby machine journal and pinportions of the workpiece successively, said method comprising:providinga phase positioning jaw in one of said pair of chucks; establishing aphase position of the workpiece with said phase positioning jaw;clamping the opposed ends of the workpiece with both of said pair ofchucks; milling with said cutter, thereby machining the journal and pinportions of said workpiece in succession except a first journal portionthat is located at a position at which said phase positioning jaw andsaid cutter interfere with each other; unclamping the one of said chucksthat is provided with said phase positioning jaw and retracting saidchuck to a position at which said jaw and said cutter no longerinterfere with each other; clamping again said opposed ends of theworkpiece with said one of said chucks so that said opposed ends of theworkpiece are again clamped by both of said pair of chucks; andthereafter milling and thereby machining said first journal portion withsaid cutter, so that all of the journal and pin portions are machinedusing a single crankshaft miller unit.
 2. A method of machining acrankshaft from a workpiece with opposed ends of the workpiece clampedby a pair of chucks using a rotating cutter to mill and thereby machinejournal and pin portions of the workpiece successively, said methodcomprising:providing a phase positioning jaw in one of said pair ofchucks; clamping the opposed ends of the workpiece with both of saidpair of chucks, with said one of said chucks in which said phasepositioning law is provided being at a position at which said phasepositioning jaw and said cutter do not interfere with each other;thereafter milling and thereby machining a first journal portion in saidworkpiece with said cutter; unclamping both of said pair of chucks andthen advancing said one of said chucks in which the phase positioningjaw is provided, and establishing a phase position of said workpiecewith said phase positioning jaw; clamping again the opposed ends of saidworkpiece with both of said pair of chucks; and thereafter milling andthereby machining all remaining journal and pin portions other than saidfirst journal portion in said workpiece, in succession with said cutter,so that all of the journal and pin portions are machined with a singlecrankshaft miller unit.
 3. A method of machining a crankshaft from aworkpiece with opposed ends of the workpiece supported by a pair ofcenters and clamped by a pair of chucks using a rotating cutter to milland thereby machine journal and pin portions successively in theworkpiece, said method comprising:providing a phase positioning jaw inone of said pair of chucks; establishing a phase position of theworkpiece with said phase positioning jaw; clamping the opposed ends ofthe workpiece with both of said pair of chucks; and thereafter millingwith said cutter, thereby machining the journal and pin portions of saidworkpiece in succession, except a first journal portion that is locatedat a position at which said phase positioning jaw and said cutterinterfere with each other; unclamping the one of said chucks that isprovided with said phase positioning jaw and retracting said chuck to asite at which said jaw and said cutter no longer interfere with eachother; clamping one of said centers that is located proximal to saidfirst journal with said one of said chucks that is provided with saidphase positioning law; and thereafter milling and thereby machining saidfirst journal portion with said cutter, so that all of the journal andpin portions are machined using a single crankshaft miller unit.
 4. Amethod of machining a crankshaft from a workpiece with opposed ends ofthe workpiece supported by a pair of centers and clamped by a pair ofchucks using a rotating cutter to mill and thereby machine journal andpin portions successively in the workpiece, said methodcomprising:providing a phase positioning jaw in one of said pair ofchucks; clamping one of said centers that is located proximal to a firstjournal portion of the workpiece with the one of said chucks that isprovided with said phase positioning jaw at a position at which saidphase positioning jaw does not interfere with said cutter, and clampingsaid workpiece at an opposite end with the other one of said pair ofchucks, thereafter milling and thereby machining a first journal portionin said workpiece with said cutter; unclamping both of said pair ofchucks and then advancing said one of said chucks that is provided withsaid phase positioning law, and establishing a phase position of saidworkpiece with said phase positioning jaw; clamping again said workpieceat the opposed ends of said workpiece with both of said pair of chucks;and thereafter milling and thereby machining all remaining journal andpin portions other than said first journal portion, in succession insaid workpiece with said cutter, so that all of the journal and pinportions are machined with a single crankshaft miller unit.